A carbon nanotube is known to have an excellent mechanical strength, thermal conductivity, and electric conductivity. It has been studied to grow a plurality of carbon nanotubes to make a carbon nanotube array and use such carbon nanotube arrays in various industrial products.
It is desired to increase the density of the plurality of carbon nanotubes in the carbon nanotube array so as to further increase the thermal conductivity and the electric conductivity. Various methods of producing a carbon nanotube array having a high density have been studied.
For example, a method of producing an oriented carbon nanotube bulk aggregate has been proposed, in which the chemical vapor deposition is used to grow a plurality of carbon nanotubes on a substrate so as to be oriented vertically to the substrate surface, then the plurality of carbon nanotubes are separated from the substrate, the plurality of separated carbon nanotubes are exposed to a liquid such as water and then dried (see, e.g., Patent Document 1).
Through this method of producing the oriented carbon nanotube bulk aggregate, one can produce an oriented carbon nanotube bulk aggregate having a density of 0.2 to 1.5 g/cm3.